A.L.1                                             PART 1 - DESCRIPTIVE
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          22A.   Electric follow-up tail
           
          (a)  General
                An electrical interconnection enables the variable-incidence
                tailplane to follow-up elevator movement.  A more power-
                ful elevator booster and a faster rate tailplane actuator are
                fitted.  Used together they give greater manoeuvrability at
                high mach numbers and the booster increases available
                elevator angle (and hence tailplane angle before jack
                stalling occurs.
                
          (b)  Selectors and indicators

                 (i)  A TAILPLANE ON/OFF switch, by means of which
                      the interconnection may be selected, is fitted on the
                      port shelf.  The tailplane indicator is so arranged to
                      indicate when the tailplane is functioning as a flying
                      control, i.e. the indicator moves when the control
                      column is deflected as well as when the trim switch
                      is actuated.
                 (ii) The circuit is so arranged that when the cover of the
                      standby trim switch is raised, both the main actuators
                      and the interconnection are isolated.
                
          (c)  Function

                 (i)  Whenever the interconnection is switched ON, and
                      electric power is available, it functions irrespective of
                      whether the elevator is in Power or in Manual.  It is
                      arranged in the form of a follow-up linkage, so that
                      for a given stick deflection and tailplane trim position
                      a predetermined relationship exists between tailplane
                      and elevator angles.  A linkage attached to the ele-
                      vator carries a switch arm, one end of which moves
                      between two micro-switches.  Movement of the ele-
                      vator relative to the tailplane energises one of these
                      switches which operates the tailplane actuator to
                      move the tailplane.  When the tailplane reaches the
                      required position the micro-switch is de-energised and
                      tailplane movement stops, leaving the elevator de-
                      flected relative to the new position of the tailplane.

                 (ii) To prevent continual hunting of the tailplane actuator,
                      the elevator has a small range of movement over
                      which the micro-switches are not selected.


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